Hydrodynamic and hydrostatic hybrid bearing and its manufacturing method

ABSTRACT

A hybrid type hydrodynamic and hydrostatic bearing and its manufacturing method are disclosed by the invention. By making use of a penetrated dynamic pressure generating groove carved on the surface of the bushing inside the housing, the processing efficiency of the tiny grooves can be substantially improved. Also, after combining the housing with the bushing, and utilizing porous material that is able to preserve a lubricant, the pressurization by gas can be added externally on the surface of the porous material. After being sealed, the gas prepress can force the lubricant to fill the interval between the bushing and shaft. The bearing can achieve the effect of lubricating and supporting the shaft.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a kind of hydro bearing and itsmanufacturing method. It is applied to small-scale spindle motors. Inparticular, it has the effect of a hydrodynamic and hydrostatic hybridtype, and it is easy to process the hydrodynamic and hydrostatic hybridbearing and its manufacturing method.

[0003] 2. Related Art

[0004] A bearing is a kind of device that is applied on rotating machineparts, and is utilized for support, to decrease friction and to accept aload. It can be used, for example, in a spindle motor. The demand forbearing precision is increasing. Generally speaking, the bearing forwhich the most precision required is the ball bearing. However, thiskind of bearing has some problems, such as noise, NRRO(Non-RepeatableRun Out) and high cost of miniaturization, and it would be unable tomeet the demands of miniaturization and precision. In order to meetthese demands, and to further reduce rotating friction, a hydro bearingwith high precision in the future, low noise and strong anti-shockcapability has been developed.

[0005] Generally speaking, there are two types of bearings: thehydrostatic bearing and hydrodynamic bearing. The hydrostatic bearing isnormally a bearing with a hydro lubricant. When the motor rotates, itutilizes hydro pressure to support its shaft. If its shaft deviates,pressure should be added from the deviated side to make the shaft returnto the correct position. However, since hydrostatic bearings usuallycontain lots of lubricat, they are not suitable for small rotatingmachine parts that require high precision.

[0006] On the other hand, the hydrodynamic bearing is a bearing withtiny grooves located at the bearing's inner aperture. Within the groovesthere is a lubricant (since the grooves is tiny, the quantity oflubricant is quite limited). When the shaft rotates, the lubricantinside the grooves is drawn and builds up hydrodynamic pressure tosupport the shaft at the centric position. However, since it ishydrodynamic, friction occurs when the shaft starts to rotate andpressure has not yet been built up. It is also very difficult to processthe inner aperture inside the bearing, and difficult to control theprocessing precision (the grooves width is usually 100 μm, and thegrooves depth is even smaller). Moreover, there are problems with thelubricant seal and lubricant filling.

[0007] Aimed at these problems with hydrodynamic bearings, manydifferent solutions have been suggested in previous cases, especiallyregarding processing methods for the tiny grooves in the bearing's inneraperture. For example, there are cutting processing, balling processing,plastic ejection, corrosion, combination and processing after cladding.However, whichever way is used for inner aperture processing, it isdifficult to increase the precision and difficult to process, andproblems relating to starting friction, lubricant seal and lubricantfilling cannot be solved. Hence, the application of bearings on thesmall active motors, like CD-ROMs and hard discs, has always beenrestricted.

SUMMARY OF THE INVENTION

[0008] The object of the invention is to solve the problems mentionedabove. It provides a kind of hydrodynamic and hydrostatic hybrid bearingand its manufacturing method. It is easy to process the inner apertureof the bearing, and also provides hydrodynamic and hydrostatic hybrideffects.

[0009] According to the invention, the hydrodynamic and hydrostatichybrid bearing contains a housing, a bushing, and an shaft. Inside thehousing there is porous material that contains a lubricant. The bushingis installed in the inner side of the housing, and has a penetrateddynamic pressure generating groove. Since it is penetrated, it is easyto process. Furthermore, since the housing is sealed after beingpre-pressurized, the lubricant can pass through the dynamic pressuregenerating groove on the bushing, and can be preserved between thebushing and the shaft. So, it can support hydrostatic pressure withoutstarting friction. When the shaft rotates, the lubricant will build uphydrodynamic pressure to support it. Because the lubricant is added fromthe porous material of the housing, pressurized and lubricant sealed, itbecomes easier to fill and seal the lubricating media.

[0010] The manufacturing method of the hydrodynamic and hydrostatichybrid bearing of the invention involves first forming a bushing, andthen forming several dynamic pressure generating groove on it. Thebushing is integrated on the housing with the porous material inside,which contains lubricant. A shaft is installed within the bushing. Thehousing is pre-pressurized and sealed. Since the bushing is a kind ofpenetrated dynamic pressure generating groove processed independently,it is very easy to process. Also, because the porous material of thehousing contains a lubricant, it is easy to fill and seal lubricant.Moreover, since the housing is pre-pressurized, it can store a suitableamount of lubricating media between the bushing and shaft. Therefore,starting friction can be avoided, and the bearing has both hydrodynamicand hydrostatic effects.

[0011] In order to provide a better understanding of the objective,structural characteristics and function of the invention, a detaileddescription with diagrams will follow.

[0012] Further scope of applicability of the invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention will become more fully understood from the detaileddescription given herein below. However, the following description isfor purposes of illustration only, and thus is not limitative of theinvention, wherein:

[0014]FIG. 1 is a diagram of the invention.

[0015]FIG. 2 is a diagram of the bushing of the invention.

[0016]FIG. 3 is a chart illustrating the static effect of the invention.

[0017]FIG. 4 is a flow chart of the invention.

[0018] FIGS. 5A˜5G are diagrams of the manufacturing method of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0019] The hydrodynamic and hydrostatic hybrid bearing and itsmanufacturing method disclosed in the invention (shown in FIG. 1)contains one shaft 10, one housing 20 and one bushing 30. The housing 20is frame shaped, contains porous material 40 inside, and can preservethe lubricant 50. One side of the housing is sealed with a sealing unit70, so as to prevent the lubricant from being exposed. In the middle ofthe porous material 40 there is a space, which can be used to installthe bushing 30. The bushing 30 with a cylinder shape is used to installthe shaft 10. The bushing 30 contains a plurality of penetrated dynamicpressure generating grooves 301 on its surface. Lubricant 50 containedin the porous material 40 can ooze through these dynamic pressuregenerating grooves 301, to achieve the effects of lubrication andsupport.

[0020] In other words, the bushing 30 utilizes a processing methoddifferent from the previously discussed well-known inner apertureprocessing methods. It uses an independent processing means ofpenetration (see FIG. 2), and then is installed in the housing 20 withporous material 40 inside. In this way, the surface of the inneraperture of the shaft 10 also contains dynamic pressure generatinggrooves 301. However, since the bushing 30 is processed independently,it makes processing easier. Also, processing methods can be morediverse. They are not restricted by the tiny size of the inner aperture,and the shape and precision of the dynamic pressure generating grooves301 are not confined. As shown in FIG. 2, the dynamic pressuregenerating grooves 301 are herringbone when it rotates opposite to theinner shaft 10. The lubricant on both sides of the dynamic pressuregenerating grooves 301 are led to concentrate in the middle and produceshydrodynamic pressure, which supports the shaft 10 in the middle of thebushing 30. However, the V-shape is given for example; the groove is notrestricted to this shape. Any shape that can serve to build uphydrodynamic pressure while rotating is suitable. Furthermore, since thebushing is processed independently, the shape of the dynamic pressuregenerating groove 301 can be more diversified.

[0021] The porous material 40 inside the housing 30 contains a lubricant50 (for example, lubricating lubricant). The porous material 40 shouldbe pre-pressurized before sealing, and then sealed by a sealing unit 70(for example, sealing glue and sealing cover, etc.) to prevent thelubricant from spilling out. Since pre-pressure 60 is added, thelubricant 50 flows out from the dynamic pressure generating groove s301of the bushing 30. It is kept between the bushing 30 and the shaft 10(because of the equilibrium between sticky force and atmosphericpressure), as shown in FIG. 3. As mentioned above, since the dynamicpressure generating grooves 301 are very tiny, just like a capillarity,the lubricant can be kept between the bushing 30 and the shaft 10. Also,the amount of lubricant 50 can be adjusted to an optimum level bycontrolling the magnitude of pre-pressure. In a normal situation, whenthe shaft has not started moving, it will provide hydrostatic protectionto avoid starting friction in the hydrodynamic bearing, and providehydrodynamic and hydrostatic hybrid effects. On the other hand, sincethe bearing uses a lubricant 50 contained in the porous material 40, itis easy to fill and seal the lubricant. Moreover, the porous material 40provides lubricating lubricant tank functions. When the lubricant 50between the bushing 30 and the shaft 10 spills out, it presses thelubricant 50 out by pre-pressure 60, to re-supply the amount oflubricant 50 between the bushing 30 and the shaft 10.

[0022] As shown in FIG. 4, in the manufacturing method of thehydrodynamic and hydrostatic hybrid bearing in the invention, thebushing is first formed (step 901), a cylinder-shaped bushing 30 withappropriate thickness is formed, and then several penetrated dynamicpressure generating groove 301 are processed on the bushing. Asmentioned above, there are many kinds of dynamic pressure generatinggrooves 301, and two groups of herringbone are shown in this figure. Acutter process, etching or plastic injection can be used as a processingmethod. Since the dynamic pressure generating grooves are formed outsidethe bushing 30, the processing method is not restricted. Here only twomethods are shown (see FIG. 5B). The burr is then eliminated to make iteasy to install.

[0023] Subsequently, the bushing 30 is integrated with the housing 20.During the manufacturing process, the bushing 30 can be inserted intothe porous material 40 (see FIG. 5D)(for example, it can be inserteddirectly or by extruding and sintering). Afterward, permeating lubricantis proceeded so as to keep lubricant 50 in the porous material 40 (seeFIG. 5E). Processing lubricant permeating lubricant is not the onlypossible method. Material that contains a lubricant can be used instead.

[0024] The shaft is installed in the bushing, and then sealed afterbeing pressurized (Step 905), as shown in FIG. 5F and FIG. 5G. Assuggested above, pre-pressure can be calculated to achieve an optimumvalue. The bearing shown in the figure is the bearing connected at thebottom (or top). However, this is not the only case. It can also beinstalled in the middle of the shaft 10. The difference is that bothsides of the housing should then be sealed (not shown in the figures).

[0025] The invention relates to a hydrodynamic and hydrostatic hybridbearing and its manufacturing method. It can achieve the followingeffects:

[0026] 1. To improve the processing efficiency of tiny grooves in theinner aperture of a small size hydro bearing.

[0027] 2. To maintain rigidity and strength of the lubricant between theaxis and bearing, and to reduce starting friction.

[0028] 3. To improve the filling method of the lubricant.

[0029] 4. To solve the leakage problem of the lubricant.

[0030] The invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A hydrodynamic and hydrostatic hybrid bearingcomprises: a housing containing a lubricant; a bushing placed in thehousing having a plurality of dynamic pressure generating grooves beingpenetrated to bushing for storing the lubricant; and a shaft rotatablyinstalled in the bushing; wherein the lubricant produces hydrodynamicpressure between the grooves and the shaft when the shaft rotatesrelative to the bushing.
 2. The hydrodynamic and hydrostatic hybridbearing as claim 1, wherein the housing comprises a porous material forstoring a lubricant.
 3. The hydrodynamic and hydrostatic hybrid bearingas claim 1, wherein the housing is applied a pre-pressure for making thelubricant pass through the grooves and preserve between the bushing andthe shaft.
 4. The hydrodynamic and hydrostatic hybrid bearing as claim3, wherein the housing further comprises a sealed unit to keep thepre-pressure.
 5. The hydrodynamic and hydrostatic hybrid bearing asclaim 4, wherein the sealed unit is a sealed glue.
 6. The hydrodynamicand hydrostatic hybrid bearing as claim 1, wherein the bushing is acylinder-shaped bushing.
 7. The hydrodynamic and hydrostatic hybridbearing as claim 1, wherein the dynamic pressure generating grooves istwo pair of herringbone grooves.
 8. The manufacturing method of thehydrodynamic and hydrostatic hybrid bearing comprises the followingsteps: forming a bushing; processing a plurality of penetrated dynamicpressure generating groove on the bushing; integrating the bushing intoa housing containing a lubricant; installing a shaft in the bushing; andapplying a pre-pressure to the housing and sealing the housing.
 9. Themanufacturing method as claim 8, wherein the bushing is acylinder-shaped bushing.
 10. The manufacturing method as claim 8,wherein the dynamic pressure generating grooves are processed by acutting processing.
 11. The manufacturing method as claim 8, wherein thedynamic pressure generating grooves are formed by an etching process.12. The manufacturing method as claim 8, wherein the dynamic pressuregenerating grooves are formed by a plastic injection process.
 13. Themanufacturing method as claim 8, wherein the dynamic pressure generatinggrooves are two pairs of herringbone grooves.
 14. The manufacturingmethod as claim 8, wherein lubricant produces a hydrodynamic pressurebetween the dynamic pressure generating grooves and the shaft when theshaft rotates relative to the bushing.
 15. The manufacturing method asclaim 8, wherein the housing contains porous material for storing thelubricant.
 16. The manufacturing method as claim 8, wherein thepre-pressure makes the lubricant pass through the grooves and be keptbetween the bushing and shaft.
 17. The manufacturing method as claim 8,wherein the housing is combined with housing by being inserted directlyinto the housing.
 18. The manufacturing method as claim 8, wherein thebushing is combined with housing by extruding and sintering.